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Question

what is advantages and disadvantages of Index-sequential files?explain it?

Answer 1

The  abbreviation,of the (D.B.M.S),stands, for the 'Data Base Management  Systems'; For the purpose, of building, the databases,an individual,normally utilizes, the generalized 'Software' package, which is known,as the 'Data Base Management Systems'(D.B.M.S); (1) As, the title,of the 'Data Base Management Systems', or (D.B.M.S),suggests, that, is used,by the individual, to build,and manage, the database,that is,it facilitates,the creation, up-gradation, organization, the maintenance, and the retrieval, of the data,from a specified database; For an example:- From, a subscriber's list, of the database,we can find out, the complete name, the address, phone number,and the subscription number, of the subscriber;

(2)The 'Important' advantages, of the Index-sequential files,could be ,given by:-

(*1)- There are seven types, of fields,which are available,in the 'Foxpro' Software, such as:-

(#1)- The 'Character'; (#2) The 'Numeric'; (#3) The 'Date'; (#4) The 'Logical'; (#5) The 'Memo'; (#6) The 'Width'; (#7) The 'Decimal';

(*2) The 'Character', is a field, which is used, to store,any character,which includes, the letters, numbers, the special symbols,and the blank spaces,and it's maximum width, is 254 character; (*4) The 'Numeric' is a field, which is used,to store,the numbers,with or without,the decimals; This field,can contain,only, the numbers,the decimal point,and the negative sign(The hyphen); For an example:- If the individual,specifies, the length, of the field,as 5,and the decimal places,as two(2),then,the maximum number,that the individual,can enter,in this field, is 99.99; (*5) The 'Date',is the field,which is used, to store, the dates; The field, of 'Date',can store,only 8 digits,in the MM/DD/YY format. Apart,from,the numbers,which,are signifying, the month,day,and the year,they are demarcated, by a slash; As,the two demarcation points,are also taken,into consideration,the total length, of the field, is eight(8),only,then; (*6) The 'Logical', is, the field,which is used,for checking, the conditions; This condition,returns,only, the two types of results, which are either,True, or False; By default, the length, of the field, is always one(1); T, or Y ,represents True,and F or N,denotes False; (*7) The 'Memo',is the field,which can store,large blocks, of text,for each record; There, is no limited field length,in the 'Memo',then;

(*8) The 'Width',is the field,which specifies, the width, of the data,ans is a number,less than,or equal to,the maximum width, of the data type;

(*9) The' Decimal', is the field, which specifies, the number, of the decimal places,in case,of the 'Numeric' field,that is,how many digits,can be placed,after, the decimal point; For an 'Example':- When, the width,is 5,and the decimal field,is 2,then the data,which is entered,could be anything,like 24567.65 and not 2456735.75,then; The seven fields,which are mentioned above,are the advantages,for using the 'Index-sequential' files;

(3) The 'Append' command:- The command, of 'Append',is used,for adding,a blank record,at the end, of the currently active database; The  Software, of 'Foxpro',allows, the individual, to append,a blank record,at the specified position,in a database,with, the following command, of:- Use<filename>

Append            

The individual,can even add, the records, from one database, to another,if the fields,have the same configuration, in both the databases;  For an example:- Let us say,the individual needs,to add,all the records,of the database, of (STUDENT.DBF), to the currently active database,in which the individual(A 'Software' Engineer),is working; Then,the command,which is given is:-

       APPEND FROM STUDENT.DBF

The command,which is given,above,adds all the records, of (STUDENT.DBF), at the bottom, of the current database. This is the major disadvantage,of an 'Index-sequential' file;  

(4)The 'INPUT' Statement:- The 'INPUT' Statement,allows, the numeric data entry,from the screen; This statement,can accept,any data type; The 'INPUT' Statement,creates the character,numeric,or the data values,which are based, on the user entry; (*1) For the 'INPUT' command,if the individual,enters,an illegal expression,then,an error message,is displayed,and the prompt message, is redisplayed; For an example, the following statement prompts,for the number,and thereafter, displays,it; (*2) The 'Sample' program,could,be given by:-

SET TALK OFF

CLEAR

INPUT "Enter the Number" TO NUM

?NUM

RETURN

(*3) The 'Output',of the program,is given by:-

Enter the Number:- 105

105

(*4)We have,to note,that:- The user,enters,the number, of 105,and the program,itself,displays it,on the next line;  

Answer 2

1.It offers both sequential and indexed searching techniques.

2.reduces the search time upto a great extent.

3.only few comparisons are required.

DISADVANTAGES

1.difficult to deletion,inserting a new record

2. random access is extremely slow

Answer 3

ADVANTAGES:

1.it is easy to implement

2.it provides fast access to the next record using lexicographic order

DISADVANTAGES

1.it is difficult to update inserting a new record may require moving a large proportion of the file

2. random access is extremely slow